Singer and The X Factor judge Demi Lovato blew her top last week when she discovered that dance routines she worked on extensively were changed at the last minute.

According to Radar Online, Demi learned that the show’s choreographer, Brian Friedman, changed the routines for contestants CeCe Frey and Willie Jones – just 10 minutes before they appeared on stage.

“Demi was pissed and told the producers this wasn’t what she’s planned and she was not putting her name to it,” says a backstage source.

“She insisted everything be changed back to what she’d planned. She’s told them all no-one is to change anything on her acts ever again. She’ll be signing absolutely everything off.”

There is also tension backstage between Britney Spears and her manager/fiancé Jason Trawick. Britney is said to be extremely stressed out about the court case currently involving her parents Lynne and Jamie Spears, who are being sued by Britney’s former “manager”, Sam Lufti, for defamation.

Britney is also said to be having relationship problems with her fiancé, who is also one of her legal conservator following her well-publicised breakdown in 2007.

Jason has been staying in a separate hotel away from Britney while she films the reality show and has been spotted partying in the company of other women without Britney.

“Their [love life] is non-existent right now. He’s more like her caretaker than her lover,” a friend told Star magazine.

For more on Britney’s personal dramas see the latest issue of the Weekly, on sale now.